Astronomical dating of a tectonic rotation on Sicily and consequences for the timing and extent of a middle Pliocene deformation phase

A detailed paleomagnetic study of long and continuous middle Pliocene sections from the Caltanisetta basin on Sicily reveals a differential clockwise rotation occurring around 3.21 Ma. The rotation appears to be a rapid event (80,000-100,000 years) which suggests that the responsible tectonic processes also occur rapidly. Its timing corresponds closely to the transition from the Trubi to the Narbone Formation at 3.19 Ma. This transition marks a major change in sedimentary environment on Sicily and in Calabria, and it is coeval, for instance, with the onset of sapropel formation in the eastern Mediterranean. Apparently it marks a synchronous and central-eastern Mediterranean-wide event. Data from the oldest sediments overlying the Tyrrhenian basement (ODP Leg 107) suggest an acceleration in opening of the Tyrrhenian Sea during the middle Pliocene. We speculate that this acceleration is related to a transpressional event in the Sicilian fold-and-thrust belt and extension which formed troughs in the foreland, the Strait of Sicily. Thrust imbrication accompanying the transpressional event on Sicily induced the middle Pliocene clockwise rotation and resulted in shallowing of the Caltanisetta basin causing the change in sedimentation regime characterised by the Trubi-Narbone transition. Following this middle Pliocene tectonic phase, no rotation took place in the southern Apennines, Calabria and Sicily until the middle Pleistocene (1.0-0.7 Ma).